The present invention relates to refastenable mechanical fastening systems, more particularly to fastening systems having free formed prongs and the process of manufacturing such fastening systems.
Refastenable mechanical fastening systems are well known in the art. Typically, such fastening systems involve two major components, a prong which is joined to a substrate and engages with a complementary second component, the receiving surface. A projection of the prong of the fastening system penetrates the receiving surface and either engages or intercepts strands or fibers of the receiving surface. The resulting mechanical interference and physical obstruction prevent removal of the fastening system from the receiving surface until the separation forces exceed either the peel or shear strength of the fastening system.
Presently, refastenable mechanical fastening systems are made by at least two general methods. One method requires a plurality of filaments, each of which may be formed into two prongs. Examples of fastening systems produced by this method are shown in U.S. Pat. No. 2,717,437, issued Sep. 13, 1955 to de Mesteral; and U.S. Pat. No. 3,943,981, issued Mar. 16, 1976 to De Brabandar which teach a raised pile of loops. Related teachings are shown in U.S. Pat. No. 4,216,257, issued Aug. 5, 1980 to Schams et al., U.S. Pat. No. 4,454,183, issued Jun. 12, 1984 to Wollman and U.S. Pat. No. 4,463,486, issued Aug. 7, 1984 to Matsuda. These references teach heating the ends of polymeric monofilaments. Other related teachings of fastening systems produced by the first method are disclosed in U.S. Pat. No. 4,307,493, issued Dec. 29, 1981 to Ochiai and U.S. Pat. No. 4,330,907, issued May 25, 1982 to Ochiai.
The second general method commonly utilized to manufacture mechanical fastening systems is to mold or extrude the systems as illustrated in U.S. Pat. No. 3,147,528, issued Sep. 8, 1964 to Erb and U.S. Pat. No. 3,594,863, issued Jul. 27, 1971 to Erb. Continuous injection molding is taught in U.S. Pat. No. 3,594,865, issued Jul. 27, 1971 to Erb.
Various prong structures are illustrated in the prior art. For example, the references discussed above teach fastening systems having stems of generally constant cross section. U.S. Pat. No. 3,708,833, issued Jan. 9, 1973 to Ribich et al. discloses a prong which is somewhat tapered from the proximal end to the distal end and perpendicularly projects from the substrate.
European Patent Application No. 0,276,970, filed Jan. 26, 1988, by the Procter and Gamble Company in the name of Scripps discloses a fastening device having a constant cross section stem oriented at an angle between about 30xc2x0 and about 90xc2x0 relative to the base.
The prior art does not show methods of manufacture which produce free formed prongs. The prior art also does not shown the structure of a mechanical fastening system wherein the prong is nonperpendicularly oriented relative to the substrate and has tapered sides.
It is an object of this invention to provide a free formed mechanical fastening system produced by a method of manufacture similar to gravure printing. It is also an object of this invention to provide a fastening system having tapered prongs which do not perpendicularly project from the associated substrate.
The invention comprises a fastening system for attaching to a complementary receiving surface. The fastening system has a substrate and at least one free formed prong comprising a base, shank and engaging means. The base of the prong is joined to the substrate and the shank is contiguous with and projects outwardly from the base. The engaging means is joined to the shank and projects laterally beyond the periphery of the shank. The shank is nonperpendicularly oriented relative to the plane of the substrate. The shank has a leading edge and a trailing edge defining a leading angle and trailing angle respectively. The leading angle and trailing angle are substantially different from each other, so that the sides of the shank are nonparallel.
The fastening system may be made according to the process comprising the steps of heating a thermally sensitive material sufficiently to reduce its viscosity for processing, and preferably to at least its melting point. A means to deposit discrete amounts of the heated material is provided. The substrate to which the material is to be joined is transported in a first direction relative to the means for depositing the material. The material is deposited on the transported substrate in discrete amounts. The discrete amount of material are then stretched in a direction having a component generally parallel to the plane of the substrate and the stretched material is severed to form a distal end and engaging means.
An illustrative and suitable, but nonlimiting, use for the fastening system produced by the process of the present invention is in conjunction with a disposable absorbent garment, such as a diaper. This example of one usage of the present invention is more fully described below.